Department of Physiology, Medical College of Georgia, Augusta, Georgia 30912, USA.
Am J Physiol Cell Physiol. 2010 Nov;299(5):C1068-78. doi: 10.1152/ajpcell.00225.2010. Epub 2010 Sep 15.
Epoxyeicosatrienoic acids (EETs), synthesized and released by astrocytes in response to glutamate, are known to play a pivotal role in neurovascular coupling. In vascular smooth muscle cells (VSMC), EETs activate large-conductance, Ca(2+)-activated K(+) (BK) channels resulting in hyperpolarization and vasodilation. However, the functional role and mechanism of action for glial-derived EETs are still to be determined. In this study, we evaluated the effect of the synthetic EET analog 11-nonyloxy-undec-8(Z)-enoic acid (NUD-GA) on outward K(+) currents mediated by calcium-activated K(+) channels. Addition of NUD-GA significantly increased intracellular Ca(2+) and outward K(+) currents in perivascular astrocytes. NUD-GA-induced currents were significantly inhibited by BK channel blockers paxilline and tetraethylammonium (TEA) (23.4 ± 2.4%; P < 0.0005). Similarly, NUD-GA-induced currents were also significantly inhibited in the presence of the small-conductance Ca(2+)-activated K(+) channel inhibitor apamin along with a combination of blockers against glutamate receptors (12.8 ± 2.70%; P < 0.05). No changes in outward currents were observed in the presence of the channel blocker for intermediate-conductance K(+) channels TRAM-34. Blockade of the endogenous production of EETs with N-methylsulfonyl-6-(2-propargyloxyphenyl)hexanamide (MS-PPOH) significantly blunted (dl)-1-aminocyclopentane-trans-1,3-dicarboxylic acid (t-ACPD)-induced outward K(+) currents (P < 0.05; n = 6). Both NUD-GA and t-ACPD significantly increased BK channel single open probability; the later was blocked following MS-PPOH incubation. Our data supports the idea that EETs are potent K(+) channel modulators in cortical perivascular astrocytes and further suggest that these metabolites may participate in NVC by modulating the levels of K(+) released at the gliovascular space.
环氧二十碳三烯酸（EETs）是由星形胶质细胞合成并释放的，已知其在神经血管耦联中发挥关键作用。在血管平滑肌细胞（VSMC）中，EETs 激活大电导、钙激活钾（BK）通道，导致超极化和血管舒张。然而，胶质衍生的 EETs 的功能作用和作用机制仍有待确定。在这项研究中，我们评估了合成 EET 类似物 11-壬氧基-十一碳-8（Z）-烯酸（NUD-GA）对钙激活钾（BK）通道介导的外向钾（K+）电流的影响。NUD-GA 的加入显著增加了周细胞星形胶质细胞内的 Ca2+和外向 K+电流。NUD-GA 诱导的电流被 BK 通道阻滞剂白屈菜碱和四乙铵（TEA）显著抑制（23.4±2.4%；P<0.0005）。同样，在存在小电导钙激活钾（SK）通道抑制剂蜂斗菜素和谷氨酸受体阻滞剂组合的情况下，NUD-GA 诱导的电流也显著抑制（12.8±2.70%；P<0.05）。在存在中间电导钾（SK）通道阻滞剂 TRAM-34 的情况下，外向电流没有变化。用 N-甲基磺酰基-6-（2-丙烯氧基苯）己酰胺（MS-PPOH）阻断内源性 EETs 的产生显著减弱了（dl）-1-氨基环戊烷-trans-1,3-二羧酸（t-ACPD）诱导的外向 K+电流（P<0.05；n=6）。NUD-GA 和 t-ACPD 均显著增加 BK 通道单开放概率；后者在 MS-PPOH 孵育后被阻断。我们的数据支持 EETs 是皮质周细胞星形胶质细胞中强有力的 K+通道调节剂的观点，并进一步表明这些代谢物可能通过调节释放到神经血管空间的 K+水平参与 NVC。
